This invention relates to brakes for automotive vehicles and particularly to supplemental, emergency brakes which can be applied in a panic situation to avoid collision and injury by bringing a vehicle quickly to a straight line stop on icy, wet or slippery ground or pavement.
When a vehicle travels on wet or icy pavement, frictional engagement between the tires and roadway needed for safe steering and braking control is reduced. Normal steering and braking maneuvers which would be safe and effective on dry pavement become extremely hazardous on slippery pavement and may throw a vehicle into a sidewise skid, causing death, severe injury and substantial property damage. Such hazardous driving conditions can exist on wet pavement at moderate and high speeds from a condition called "planing" where the tires are supported on a slippery water film and have little or no frictional engagement with the pavement.
Restraint devices such as seat and shoulder belts, head rests, and air bags, are effective safety accessories and have saved many lives and reduced the number and severity of injuries in head-on and rear end collisions, major hazards for which they were developed. However, they cannot prevent collision damage to the vehicle and are relatively ineffective to prevent injuries when a vehicle spins or skids sidewise out of control. A spinning or skidding car striking a curb sidewise can jar a door open and throw passengers onto the ground an instant before the car rolls over on them.
Supplemental emergency brakes have been proposed for actuation in a panic situation to avert an imminent collision. These take the form of skids, feet, toothed wheels, or the like, with driver control means for suddenly engaging them with the ground. Examples are shown in U.S. Pat. Nos. 2,049,357 and 3,042,150 (spiked feet); U.S. Pat. Nos. 3,799,293 and 3,994,369 (friction skids); and U.S. Pat. No. 2,608,274 (spiked shoes or backwardly-rotating wheels). Except for U.S. Pat. No. 3,799,293 where a single such device has been fitted only at the rear of the vehicle, none of them have been effective to avoid a spin or side skid or to straighten the vehicle once the spin or skid begins. Further, in a device such as shown in U.S. Pat. No. 3,799,293, if it is actuated when the vehicle has spun completely around, the resulting sudden stopping of the rear end can dangerously accelerate the spin instead of correcting it.